Characterization of H2-Splitting Products of Frustrated Lewis Pairs: Benefit of Fast Magic-Angle Spinning |
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Authors: | Alexander A Malär Dr Shunxi Dong Dr Gerald Kehr Prof Gerhard Erker Prof Beat H Meier Dr Thomas Wiegand |
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Institution: | 1. Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland;2. Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, 48149 Münster, Germany |
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Abstract: | Proton spectroscopy in solid-state NMR on catalytic materials offers new opportunities in structural characterization, in particular of reaction products of catalytic reactions such as hydrogenation reactions. Unfortunately, the 1H NMR line widths in magic-angle spinning solid-state spectra are often broadened by an incomplete averaging of 1H-1H dipolar couplings. We herein discuss two model compounds, namely the H2-splitting products of two phosphane-borane Frustrated Lewis Pairs (FLPs), to study potentials and limitations of proton solid-state NMR experiments employing magic-angle spinning frequencies larger than 100 kHz at a static magnetic field strength of 20.0 T. The 1H lines are homogeneously broadened as illustrated by spin-echo decay experiments. We study two structurally similar materials which however show significant differences in 1H line widths which we explain by differences in their 1H-1H dipolar networks. We discuss the benefit of fast MAS experiments up to 110 kHz to detect the resonances of the H+/H? pair in the hydrogenation products of FLPs. |
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Keywords: | dihydrogen splitting frustrated Lewis pair 110?kHz MAS NMR spectroscopy proton detection |
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